func (b *atomicOffAddr) StoreUnmark(markedAddr, newAddr uintptr) {
	b.a.CompareAndSwap(-int64(markedAddr-arenaBaseOffset), int64(newAddr-arenaBaseOffset))
}

// StoreMarked stores addr but first converted to the offset address
// space and then negated.
func (b *atomicOffAddr) StoreMarked(addr uintptr) {
	b.a.Store(-int64(addr - arenaBaseOffset))
}

// Load returns the address in the box as a virtual address. It also

	// decreases, even if the value we loaded is stale, the actual
	// value will never be larger.
	searchAddr, _ := s.searchAddrForce.Load()
	if (offAddr{searchAddr}).lessThan(offAddr{addr}) {
		s.searchAddrForce.StoreMarked(addr)
	}
}

// nextGen moves the scavenger forward one generation. Must be called
// once per GC cycle, but may be called more often to force more memory
// to be released.
//